Well plugging apparatus and method

ABSTRACT

An apparatus for plugging a burning or gushing well comprises a hollow tubular plug body (20) sized for insertion into a well casing (112). Provided on the plug body are a retainer module (54) for retaining the plug within the well casing; a sealing sleeve (46) provided for forming a seal between the plug body and the well casing; and a valve assembly (50) for selectively closing a hollow internal passageway of the tubular plug body. The plug body is loaded on a gantry assembly (21), which in turn is carried by a shielded vehicle (24). At the base of the gantry assembly are provided an alignment assembly (37) for aid in approach to the well casing and a cutter assembly (40) for sawing off inordinately protruding casings. In one embodiment, a protective break-away shell (118) circumferentially surrounds at least a portion of the plug body.

BACKGROUND

1. Field of Invention

This invention pertains to the method apparatus and system forextinguishing and capping burning or gushing oil, gas, geothermal, orwater wells.

2. Related Art and Other Considerations

Few things on earth are as awesome and dangerous as oil or gas wellfires. The extremes of temperature, pressure, noxious/toxic fumes,acidic impurities in crude oil, slippery conditions, limited visibility,and difficult site conditions combine to make extinguishing and cappinga burning or gushing well very difficult and hazardous. Manydevelopments such as automatic shut-off valves, safety valves andblowout preventers attempt to eliminate wild wells before they get outof control. These methods certainly reduce the risk of wild wells, butseveral well fires still occur in an average year throughout the world.They may be caused by static electricity, lightning, human error, higherpressure than anticipated, accidents, sabotage, or other reasons.

The standard methods of oil well fire-fighting and capping weredeveloped in the 1920's or earlier. The most popular and universalextinguishing method consists of driving a crane-like piece of equipmentclose to the burning well so that it suspends a container of hundred ofpounds of high explosives near the apex of the flame. The equipmentoperator then dismounts his vehicle and immediately vacates the area ofthe well. The explosive is detonated and (usually) sufficiently deprivesthe fire of oxygen to extinguish the fire. This leaves a gushing wellwith a high danger of reignition. Gushing wells are usually capped byseveral men going to the wellhead and connecting a control valve (e.g.,Christmas Tree valve). The valve connection is accomplished mostly byhand with the aid of some tools and equipment, but the men are coveredwith crude oil and struggle against pressures that may exceed 20,000psi. If a gushing well reignites from a static spark, heat, orlightning, all personnel in the vicinity who are covered with oil areendangered by a possibility of being instantly incinerated.

As a result of the oil field fires in Kuwait in 1991, several newmethods of extinguishing well fires have been used with varying successsuch as liquid nitrogen injection and blowing out the fire with theexhaust of a jet engine. However, they all place people with onlylimited protection in close proximity to the fire and all leave agushing well to be capped. Additionally, they are limited when anotherburning well is close by. The only method that extinguishes and "CAPS" awell simultaneously consists of dropping a heavy dome over the wellhead.The dome is only a temporary cap that must be removed to place the wellinto production.

Up until now, no method has been able to extinguish, cap, and place awell into production in a matter of minutes and without exposing peopleto crude oil, heat, flame, fumes, and slippery conditions.

Accordingly, it is an object of the present invention to provide amethod, apparatus, and system for extinguishing and capping burning orgushing wells with maximum safety and minimum exposure of personnel.

An advantage of the present invention is the provision of a method,apparatus, and system that renders a well usable a short time afterplugging.

Another advantage of the present invention is the provision of methodand apparatus for accomplishing the entire plugging operation by remotecontrol from a distant position of safety, thus not endangering humanlife.

Yet another advantage of the present invention is the provision ofapparatus and method that are operative on damaged well casings aboveground, and even on casings that may be broken off below ground level.

Still another advantage of the present invention is the provision ofapparatus and method that extinguishes and caps a well in a singleprocess.

A further advantage of the present invention is the provision ofapparatus and method which does not require explosives or an inordinateamount of time.

An even further advantage of the present invention is the provision ofapparatus and method that extinguishes and caps a well right next toanother burning well.

Another advantage of the present invention is the provision of apparatusand method which are more economical than alternative methods andequipment.

Another advantage of the present invention is the provision of apparatusand method which utilize components which are simple and reliable.

SUMMARY

This invention is a remote controlled, protected vehicle with anattached plug insertion apparatus and specially designed hot plug which,when inserted into a well casing, locks itself to the well casings'interior, seals itself to the well casing's interior, and closes itsintegral valve to shut off fluid flow and extinguish the fire, if any.The entire system can withstand the high heat, flame, pressure, andforces exhibited by uncontrolled wells. It does not endanger human lifebut does put the well rapidly into production. The system isself-aligning and can cut off a damaged well casing, if necessary.

The apparatus for plugging a burning or gushing well comprises a hollowtubular plug body sized for insertion into a well casing. Provided onthe plug body are a retainer module for retaining the plug within thewell casing; a sealing sleeve provided for forming a seal between theplug body and the well casing; and a valve for selectively closing ahollow internal passageway of the tubular plug body. The plug body isloaded on a gantry assembly, which in turn is carried by a shieldedvehicle. At the base of the gantry assembly are provided an alignmentassembly for aid in approach to the well casing and a cutter assemblyfor sawing off inordinately protruding casings. In one embodiment, aprotective break-away shell circumferentially surrounds at least aportion of the plug body.

In accordance with a method of the invention, the plug body is insertedinto the well casing and locked in place by actuating the retainermodule. A seal is then formed between the peripheral surface of the plugbody and the well casing. The hollow internal passageway of the tubularplug body is selectively closed by operation of the valve assembly,thereby extinguishing the fire.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments as illustrated in the accompanyingdrawings in which reference characters refer to the same partsthroughout the various views. The drawings are not necessarily to scale,emphasis instead being placed upon illustrating the principles of theinvention.

FIG. 1A is a side view of apparatus for plugging a burning or gushingwell according to a first embodiment of the invention, the apparatusbeing carried upon a first type of military vehicle.

FIG. 1B is a side view of the apparatus of FIG. 1A being carried upon asecond type of military vehicle.

FIG. 1C is a side view of the apparatus of FIG. 1A being carried upon acivilian vehicle such as a bull dozer or front-end loader.

FIG. 2 is a side view, partially sectioned, of a plug body of anembodiment of the invention.

FIG. 3 is a detailed side view, partially sectioned, of a cable-operatedball valve included in a well plug of the invention.

FIG. 4 is a side view of one embodiment of a retainer included in a wellplug of the invention.

FIG. 4A is a partially sectioned side view of the retainer of FIG. 4.

FIG. 4B is a sectioned view taken along line 4--4 of FIG. 4A.

FIG. 5 is a detailed side view, partially sectioned, of a sealing sleeveusable in a well plug of the invention.

FIG. 6A is a schematic top view of an alignment assembly usable with awell plug of the invention, the alignment assembly being in a operativeorientation.

FIG. 6B is a schematic top view of the alignment assembly of FIG. 6A ina storage orientation.

FIG. 7A is a side view, partially sectioned, of a plug body of a secondembodiment of the invention.

FIG. 7B is a cross-sectional view of the plug body of FIG. 7A takenalong line 7--7.

FIG. 8 is a partial longitudinal cross-section of another embodiment ofa retainer usable in a well plug of the invention.

FIG. 9 is a partial longitudinal cross-section of yet another embodimentof a retainer usable in a well plug of the invention.

FIG. 10 is a sectional view of the apparatus of FIG. 1A taken along line10--10.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an installation apparatus 18 for installing a plug 20(also known as the "hot plug") in a casing 112 of a burning oil or gaswell or gushing water, geothermal, oil or gas well. The structure of thehot plug 20 per se will be described in further detail with reference toFIGS. 2-5.

As shown in FIG. 1A, the installation apparatus consists of gantryassembly 21 which includes an insertion ram 22 (also known as a pluginsertion means); a track driven, self-propelled, heat-shielded vehicle24; a heat shield 30 carried by the vehicle 24; and, a plurality ofconnecting arms 31 for connecting the gantry assembly 21 to the heatshield 30 and ultimately to the vehicle 24 by struts 140 and 142. Theconnecting arms 31 comprise steel struts. Although not shown as such, itshould be understood that there are left and right lower struts 31 aswell as left and right upper struts 31, and left and right struts 140and 142.

On a front surface thereof, the heat shield 30 bears a video camera 32within a protective enclosure 34. The enclosure 34 has a transparentpyrex window 36 that is continuously cleaned on its exterior by apressure jet spray of non-combustible gas such as nitrogen. In thisregard, a spray port 35 is provided above the pyrex window 36 and isconnected by hoses to a cylinder of compressed gas or a motor drivenpump (mounted either in the enclosure 34 or on the vehicle 24) forsupplying the non-combustible gas.

At its base, the gantry assembly 21 carries an alignment assembly 37including an alignment fork 38, as well as a casing cutter 40. Thecasing cutter includes a cut-off saw 41. The alignment assembly 37 andthe casing cutter 40 are described in greater detail hereinafter withreference to FIGS. 6A and 6B.

The heat shield 30 comprises heavy steel plates which form anessentially inverted box-like enclosure having front, back, left side,right side, and top walls. The external surface of the heat shield isprovided with a reflective coating such as aluminizing to reduce itsheat absorption even further.

The heat shield 30 has supporting members of steel and an access door128 located on its left side near its rear. The heat shield 30 ismounted on the vehicle 24 by a plurality of struts, including rearsupport struts 124. Rear support struts 124 include hydraulic cylinders125 which allow the heat shield 30 to be raised or lowered. There issufficient structural bracing (not shown on FIG. 1A for sake of clarity)internally in the heat shield 30 to maintain a rigid, box likestructure.

The gantry assembly 21 comprises two heavy gantry vertical frame membersor tower 144; two gantry guide rods 138 (only one being shown in FIG.1A, the other being behind the rod shown in FIG. 1A); a very heavyhydraulic cylinder 136; a rigid horizontal gantry base plate 146; ahorizontal gantry top plate 147; and, movable plug guides 148. Theplates 147 and 146 are attached to (or integral with) the gantryvertical frame members 144. The lower ends of the guide rods 138 extendbelow the base plate 146 and provide for rigid connection of thealignment assembly 37 and the cutter assembly 40. The alignment assembly37 and cutter assembly 40 are described in further detail with referenceto FIGS. 6A and 6B.

FIGS. 1B and 1C show essentially identical installation apparatuses 18and plugs 20, and primarily differ in the type of vehicle upon which theheat shield 30 and installation apparatus 18 are mounted. In particular,FIG. 1B shows the installation apparatus 18 and heat shield 30 carriedon an alternate type of military vehicle 26 (such as a military tank orself-propelled artillery piece), while FIG. 1C shows the installationapparatus 18 and heat shield 30 carried on a civilian vehicle 28 (suchas a bull dozer, front-end loader, or other standard, commonlyavailable, piece of construction equipment of sufficient weight). FIGS.1B and 1C employ the same reference numerals as FIG. 1A for illustratingidentical or comparable structure. Various structural details not shownin FIGS. 1B and 1C are understood with reference to FIG. 1A.

FIG. 2 shows a hot plug 20 inserted, locked, and sealed in a well casing112. The plug 20 includes an essentially hollow cylindrical plug body 42comprised of two sections, in particular lower plug body 42A and upperplug body 42B. Plug body 42 is formed from a heavy steel and is of ahollow tubular shape having an internal passageway therein. Plug body 42has a guide nose or guide point 43 at a lower end thereof. Also includedin the plug body is a sealing module or sealing sleeve 46 and a ballvalve 50. The sealing module 46 is described in more detail withreference to FIG. 5, while the ball valve is described in more detailwith reference to FIG. 3. Whether or not specifically statedhereinafter, it should be understood that portions of the plug body 42above the ball valve assembly 50 are of the upper plug body 42B, whileportions of the plug body below the ball valve assembly 50 are of thelower plug body 42A.

The guide point 43 is comprised of a plurality of guide struts 44 whichmeet together to define a conical structure at a lower point. Since thestruts 44 are unconnected other than at the lower point, the struts 44provide a conical volume 45. The guide point 43 serves not only to startthe hot plug 20 easily into the well casing 112 upon insertion, but alsocenters the plug body 20 and thereby protects the sealing module 46 andball valve 50 from catching or snagging on the top of the well casing112. In addition, the guide point 43 allows a maximum fluid flow withminimum drag force through the open center of the hot plug body 42, thusassuring a minimum insertion force requirement.

Above the guide point 43 in FIG. 2 is the sealing module 46. The sealingmodule 46 (shown in more detail in FIG. 5) comprises an elastomeric,high temperature resistant, tubular sleeve or bladder 47. The sealingsleeve 47 is securely held in place on the outer peripheral surface ofthe plug body 42 by steel retaining collars 48 which both seal it to thehot plug body 42 and prevent relative longitudinal motion. As describedhereinafter with reference to FIG. 5, the sleeve 47 is inflatable withhydraulic fluid supplied through a high pressure hydraulic fluid line49.

Above the sealing module 46 in FIG. 2 is a cable operated ball valveassembly 50, illustrated in more detail in FIG. 3. A ball valve case 52is drilled and tapped for connection of the high pressure hydraulicfluid line 49 which passes through the ball valve assembly 50 and whichfurnishes hydraulic fluid for inflation of the sealing module 46.

Above the ball valve assembly 50 in FIG. 2 is a retainer module 54. Inthe embodiment illustrated in FIGS. 2, 4, 4B, and 4A, the retainermodule 54 comprises three heavy jaw assemblies 70A, 70B, and 70C thatbite into the well casing's 112 interior when the retainer module 54 isactivated. As shown in FIG. 4B, the jaw assemblies 70A, 70B, and 70C arepositioned around the periphery of the plug body 42, with each jawassembly extending just shy of one third the circumference of the plugbody and small gaps or spaces 73 being provided between the jawassemblies. The jaw assemblies 70A, 70B, and 70C each have teeth 71provided thereon and are borne by a fluid bladder 72 that inflates withhydraulic fluid when activated. Inflation of the bladder 72 causes thejaws 70 to engage the well casing 112. Two axial collars 74 hold theretainer module 54 in place on the plug body 42.

Depending on the pressure expected at a wellhead, there may be two ormore retainer modules 54 used on a hot plug 20. The retainer module 54and two alternate configurations are described in further detail withreference to FIGS. 4, 8, and 9.

Near the top of the hot plug 20, and above the portion of the hot plug20 that is inserted into the well casing 112, is a steel radial arm orprotective sleeve 56. All hydraulic lines run through the sleeve 56between the members 144 of the insertion ram 22 and ultimately throughthe heat shield 30 to the vehicle 24, 26, or 28.

At the very top of the hot plug is a top flange assembly 122 which isscrewed onto the hot plug body 42 with standard pipe threads. The flangeassembly 122 mates with the insertion ram 22 to hold the hot plug 20 inplace during insertion and allows full inside diameter fluid flowthrough the hot plug 20 and insertion ram 22. The flange assembly 122can be removed for connection of the hot plug 20 to a production pipeline after the hot plug 20 is inserted, locked, sealed, and the ballvalve 50 is closed. Upon connection to production piping the ball valve50 may be easily reopened, which reopening places the well immediatelyinto production.

FIG. 3 shows in more detail the cable operated ball valve assembly 50.The case 52 of the ball valve consists of two halves, only one halfbeing shown by virtue of the cross section illustration of FIG. 3. Thehalves of the case 52 bolt together with four high strength steel bolts123. The mating faces of the case 52 halves are precision machined toeffect a seal without the use of gaskets. The lower ends of the case 52halves having tapering surfaces 53 on their exterior to prevent themfrom snagging on the well casing 112 during insertion. The axial ends ofthe case 52 halves are internally threaded for attachment to upper andlower plug body sections 42B and 42A, respectively. One case 52 half isdrilled from end to end (i.e., from top to bottom) for passage of thehydraulic fluid line 49 to the sealing module 46 for its activation. Thecase 52 halves may be welded together in addition to being bolted toeffect greater strength and seal.

The ball valve assembly 50 includes a ball 58 of precision machinedsteel. The ball 58 has protruding trunions 64 on opposite sides whichfit into trunion sockets in the valve case 52 halves and which allow theball 58 to pivot smoothly about the trunion's 64 axis. Attached to theball 58 are two steel cables 60 & 62 which serve to rotate the ball 58to a closed position (cable 60) or open position (cable 62) whentensioned. Cable 60 has its own raceway 68 machined into the side of theball, and cable 62 has its own raceway 66 machined into the case 52half. A central axial opening through the ball 58 allows (when the ballis rotated to its open position) for a maximum, free flowing insidediameter for any given outside diameter. The ball 58 may or may notutilize sealing rings to effect a seal in its closed position dependingon the anticipated conditions of use. A pivoted lever (not shown) nearthe top of the hot plug provides for one cable 60 or 62 to be slackenedwhenever the other cable 62 or 60 respectively is tensioned. Cable 60 istensioned by a small hydraulic cylinder (not shown) located near the topof the hot plug 20.

FIG. 4A is a lateral view, partially sectioned, of the retainer module54 which is built around the plug body upper section 42B. As explainedabove, the retainer module 54 consists of three toothed jaws assemblies70A, 70B, and 70C placed circumferentially around the hydraulic bladder72. Both the hydraulic bladder 72 and the jaws 70 are held in place byretainer rings 74 at their upper and lower ends. The retainer rings 74are crimped tightly in place and their outer edges are weldedcircumferentially to the hot plug upper body 42B. A small steel tube 76supplies hydraulic fluid to an annular space 78 between the hot plugupper body section 42B and the hydraulic bladder 72. The application ofhydraulic fluid inflates the bladder and causes the jaws 70 to be drivenradially outward to firmly engage the inside surface of the well casing112.

As shown in FIG. 4B, the spaces 73 between the jaws 70 allow the ballvalve's 50 operating cables 60 and 62 to travel up past the jaws 70. Thethird space between the jaws 70 is utilized for placement of thehydraulic line 49 which operates the inflation of the sealing module 46.The top ends of the hydraulic fluid supply tube 76 and line 49 havecheck valves (not shown) installed to prevent deflation due to loss ofpressure anywhere in the hydraulic system and may operate at pressuresthat are stepped up from the output pressure of the vehicle if necessaryfor locking and sealing against the extremely high pressures found insome wells.

FIG. 8 is a lateral cross-section showing an alternate locking orretainer assembly 80 that employs multiple levels of pivotal engagementlevers 82 in various planes and of sufficient number to assure thelocking against a stated design pressure. The levers 82 extend throughslots 81 provided in the plug body upper section 42B. The engagementlevers 82 have cam shaped outer lower profiles that allow them to beeasily inserted into the well casing 112. Their inner ends are longenough to prevent their travel past a locked position and have steelcables 83 attached that travel up the interior of the upper hot plugbody 42B. The multiple cables are joined as necessary and travel over anunillustrated pulley at the top of the hot plug 20 to a small hydrauliccylinder (not shown) on the exterior of the upper hot plug body 42B thatapplies or releases tension to the cables 83.

FIG. 9. is a lateral cross-section showing yet another alternateretainer or locking assembly 84. This assembly utilizes spring 88operated toothed cam locks 86 spaced alternately around ring 85 betweenattachment brackets (not shown) which secure the ring to the upper hotplug body 42B. As few as eight cam locks 86 may be on a ring 85 and moremay be provided for larger diameter hot plugs 20. A sufficient number ofrings 85 are provided, as required, to resist the expected pressure ofthe well. Exterior cable and hydraulic lines, although not shown onFIGS. 5, 4A, 8, and 9, pass between engagement levers 82 or toothed camlocks 86 to prevent interference. Exterior cable and hydraulic lines areprotected by steel tubing throughout their lengths.

FIG. 5 is a lateral cross-section of the sealing module 46 showing thelower hot plug body 42A, the elastomeric, high temperature resistant,tubular sleeve section 47 in its inflated position, two retainingcollars 48, fluid reservoir 96, and hydraulic fluid supply tube 49. Theretaining collars 48 are crimped tightly in place and their outer edgesmay be welded to the lower hot plug body 42A to provide a secure sealand to prevent sliding along the lower hot plug body 42A under extremeloading conditions. The lower hot plug body 42A is slotted or channeledas at 92 to provide an access space for the fluid supply tube 49 whichis brazed into place for a complete seal and the surface is groundsmooth and/or polished so that the upper collar 48 does not crush thetube 49 and effects a secure high pressure seal. It should be understoodfrom FIG. 5 that when hydraulic fluid passes through hydraulic fluidsupply tube 49 the sleeve section 47 inflates by virtue of fluidentering the reservoir 96 until the exterior surface of the bladder 47seals tightly against the interior of the well casing 112. The pressureof the hydraulic fluid supplied is stepped up to a pressure sufficientlygreater than the fluid spewing from the uncontrolled well to generate acomplete seal.

FIG. 6A is a top view partially sectioned, showing both the alignmentassembly 37 and the cutter assembly 40. FIG. 6A shows the cutterassembly 40 with power cable cut-off saw 41 in an operating position andhaving completed the cutting-off of a well casing 112.

The alignment assembly 37 comprises the alignment fork 38. The alignmentfork 38 has two heavy vertical rods 150 that attach to the lower ends ofthe gantry guide rods 138. The rods 150 hold the alignment fork 38rigidly in place. The alignment fork 38 has two fork members 160A and160B connected to provide the fork with a V-shape. A plurality ofsensors 108 are provided on facing surfaces of the two fork members160A, 160B. As shown in FIG. 6A, the two fork members 160A, 160B areoriented to accommodate the well casing 112 therebetween.

The multiple sensors 108 indicate upon contact with well casing 112 orwith a high pressure fluid flow if the well casing 112 does not extendabove ground level. In one embodiment, the sensor indications aredisplayed on a video display device within the vehicle for observationby the vehicle operator. In an alternate embodiment, particularly thecase of remote control operation, the sensor indications are displayedat a remote control console. Electrical connection lines 109 (only someof which are shown) from individual sensors 108 pass through thealignment fork 38 and join to form a cable which passes through athermally protective conduit 116 to the vehicle 24.

The cutter assembly 40 includes a pivoting horizontal plate 162 shapedin the form of a trapezoid. At one of its back corners the cutterpivoting plate 162 carries a pivot collar 164 which rotatably surroundsa corresponding one of the vertical rods 150. At another of its backcorners the cutter pivoting plate 162 carries a half-collar 166 whichbears against a corresponding other one of the vertical rods 150 whenthe cutter assembly 40 is in its utilization configuration. Thehalf-collar 166 has a radial connection flange 168 which has a pin holetherein for receiving a connection pin 152. Further, the plate 162 has afirst of three pulley wheels 102 rotatably mounted thereon.

The cutter plate 162 has two horizontal support struts 104 which extendtherefrom in a V-shaped cantilevered fashion. Intermediate segments ofthe struts 104 are connected by a cross-bar and spring tensioningassembly 106 to provide sufficient force for maintaining separation ofthe struts 104. On their distal ends, the support struts 104 each haveone of the other two of the three pulley wheels 102 rotatably mountedthereon. The pulley wheels 102 are mounted in a horizontal plane so thata multistrand abrasive cable 98 (comprising saw 41) can be entrainedthereabout.

The cutter assembly 40 slides vertically downward onto the left verticalrod 150. A first hydraulic cylinder 110 is anchored to the fork member160A and has its piston attached to the connection flange 168 by the pinconnection 152. The hydraulic cylinder 110 extends until stopped bycontact with the right vertical rod 150 of the alignment fork 38,thereby moving the power cable cut-off saw 41 into its operatingposition and maintaining the saw 41 in that utilization position. Whenthe hydraulic cylinder 110 retracts, it moves the power cable cut-offsaw 41 into its swing-away, or stored, position.

The abrasive cable 98 travels on the three silicone rubber lined pulleywheels 102, two of which are held in place by pulley support struts 104and spring tensioner 106. The third pulley 102, which is the drivepulley, is attached to and driven by a hydraulic motor 100. Thehydraulic motor 100 is served by hydraulic fluid supply and return linesthat travel to the power cable cut-off saw 41 from the vehicle (24, 26,28) in a thermally protected flexible conduit 114.

FIG. 6B is a schematic top view of the alignment fork 38 with the powercable cut-off saw 41 attached and shown in its swing-away or storedposition (with the swing-away operating cylinder 110 shown disconnectedfor illustration purposes only). Also shown are the hydraulic supply,return, and control lines 114 which have thermal protection and carryhydraulic fluid from the vehicle to the hydraulic motor and return, aswell as the thermally protected sensor lines 116 which carry sensorindications to a video screen mounted within the vehicle or,alternatively, are sent by a computer on board the vehicle to a remotecontrol console.

FIG. 7A is a lateral view, partially sectioned, of the lower part of ahot plug assembly 20 showing a protective break-away shell 118 installedfor additional thermal protection. The shell 118 may be of potter'sclay, ceramic, or other heat resistant material. The break-away shell isinstalled before the guide point 43 is welded in place and extendsradially beyond the guide point 43 so that contact with the top of thewell casing 112 will cause it to break easily and have its piecescarried away by the stream of well fluid during the insertion process.

FIG. 7B is a cross-sectional view of the hot plug taken through themiddle of the sealing module 46 with a protective break-away shell 118installed. There is an air space 170 between the sealing sleeve 47 andthe protective break-away shell 118. Formed-in fault lines 120 whichassist in breaking are shown in FIG. 7B. Also shown is the lower hotplug body 42A.

FIG. 10 is a horizontal cross section of the gantry 21 lookingdownwardly from above. FIG. 10 shows movable plate 174, which travels upand down, being guided by guide rods 138 and vertical frame members 144and driven by the double acting hydraulic cylinder 136. Plate 174engages flange 122 at the top of the hot plug 20, which is held securelyby holding plates 176 and 178 when they are pivoted to their closedpositions as shown in FIG. 10.

OPERATION

The well plugging operation begins with collection of data. Data arecollected on the inside diameter of the well casing, site conditions,pressure encountered in this particular field (or, if not available, inthe general area), availability of safety and support services, and avariety of other information. From the data an operational plan isdeveloped and implemented. A hot plug 20 of the correct size range forthe well casing is loaded onto the gantry assembly 21. The saw 41 isinstalled, if needed. The vehicle and all equipment are assembled at thesite, checked and tested, fueled, and made ready.

If obstructions are present, or the casing 112 extends to a troublesomeheight, the power cable cut-off saw 41 is pivoted to its utilizationconfiguration by activation of the cylinder 110.

The vehicle with heat shield 30, gantry assembly 21, hot plug 20 andalignment assembly 37 in place is moved up the well head. The vehiclemoves straight ahead so that the alignment assembly 37 contacts the wellcasing 112. Maneuvering of the vehicle is aided by the sensor displaywhich receives inputs from the sensors 108. The sensory input enablesthe operator to align perfectly the alignment assembly 37, and hence theentire gantry assembly 21 and the plug 20, over the well casing 112 orcenter of fluid flow.

When alignment is reached (in less than one minute), the motor 100 isactivated to power the cable saw 41. The vehicle is driven to push thesaw 41 into the casing 112 (e.g., to the left in FIG. 1) until the saw41 has eaten completely through the casing 112.

Upon completion of the casing 112 cut-off operation, the hydrauliccylinder 136 of the gantry assembly 21 is activated to push the hot plug20 into the well casing 112. The hot plug 20 is then locked into thewell casing by activating its locking or retaining module 54. Then,hydraulic fluid is supplied to the bladder 47 of the sealing module 46for sealing the plug 20 against the interior surface of the well casing112. The ball valve assembly 50 is then closed very slowly in order tominimize the hammer effect.

After installation, the hot plug 20 can then either be left in place asa temporary cap; be removed and replaced by a "Christmas Tree" type ofcontrol valve; or be epoxy grouted or welded permanently in place andconnected to production piping (after removing the flange assembly 122).When permanently secured and connected, the ball valve assembly 50 maybe re-opened to place the well rapidly into production.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it will be understood bythose skilled in the art that various alterations in form and detail maybe made therein without departing from the spirit and scope of theinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An apparatus forplugging a burning or gushing well, the apparatus comprising:a tubularplug body sized for insertion into a well casing, the plug body having aperipheral surface and a hollow internal passageway; a retainer providedon the plug body for retaining the plug within the well casing; asealing sleeve provided at least on the peripheral surface of the plugbody for forming a seal between the peripheral surface of the plug bodyand the well casing; a valve formed in an interior of the plug body forselectively closing the hollow internal passageway of the tubular plugbody.
 2. The apparatus of claim 1, wherein the sealing sleeve comprisesan annular bladder pressurizable with an hydraulic fluid, first andsecond axial ends of the annular bladder fixedly mounted on the plugbody, an interior portion of the annular bladder being fillable with thehydraulic fluid.
 3. The apparatus of claim 2, further comprising ahydraulic line having a first end connected to the annular bladder and asecond end connected to a source of hydraulic fluid, at least a portionof the hydraulic line extending through a channel formed in the plugbody.
 4. The apparatus of claim 1, wherein the valve is a ball valve,wherein the ball valve has a first end of at least one valve cableconnected thereto for actuating the valve into an opened and a closedposition for respectively opening and closing the internal passageway ofthe plug body, and wherein the valve cable at least partially extendsthrough a channel formed in the plug body whereby a second end of thevalve cable is remotely connected to a valve actuator.
 5. The apparatusof claim 1, wherein the retainer comprises a plurality of finned jawsformed on the peripheral surface of the plug body.
 6. The apparatus ofclaim 1, wherein the retainer comprises:a flexible annular bladderattached about the plug body; a jaw assembly attached to an exteriorperipheral surface of the flexible annular bladder, whereby the jawassembly radially bears against an interior surface of a well casingupon expansion of the annular bladder due to introduction of a fluid inthe bladder.
 7. The apparatus of claim 6, wherein the jaw assemblycomprises a plurality of jaw members positioned at circumferentiallyspaced apart locations on the flexible annular bladder, with a gap beingprovided between the jaw members in order to accommodate hydraulic linesextending axially along the plug body.
 8. The apparatus of claim 6,wherein a plurality of finned jaws formed on a peripheral surface of thejaw assembly.
 9. The apparatus of claim 1, wherein the retainercomprises a pivotal blade, the pivotal blade having a first end whichselectively bears against an interior surface of the well casing and asecond end positioned within the internal passageway of the plug bodywhereat the second end is connected to an actuator, the peripheralsurface of the well plug having an opening formed therein through whichan intermediate portion of the pivotal blade extends.
 10. The apparatusof claim 9, wherein the second end of the pivotal blade is connected toa first end of a blade cable, and wherein the blade cable extendsthrough a channel formed in the plug body, a second end of the bladecable being remotely connected to a retainer actuator.
 11. The apparatusof claim 1, wherein the retaining means comprises a plurality of pivotaltoothed members mounted on the plug body, the toothed members beingpivotal to a first position for insertion of the plug body into the wellcasing and to a second position for engagement against the interiorsurface of the well casing.
 12. The apparatus of claim 1, furthercomprising:a gantry assembly upon which the plug body is suspended andtransported to the well casing, the gantry assembly including pluginsertion means mounted on the gantry assembly for inserting the plugbody into the well casing.
 13. The apparatus of claim 12, wherein thegantry assembly comprises a vertically erect tower, and wherein the pluginsertion means is hydraulically operated for inserting the plug bodyinto the well casing.
 14. The apparatus of claim 12, furthercomprising:a shield for at least partially enclosing a vehicle uponwhich the gantry assembly is carried; at least one connecting armcomprising the gantry assembly for attaching the gantry assembly to thevehicle upon which the gantry assembly is carried.
 15. The apparatus ofclaim 14, wherein the shield has a transparent widow formed thereinthrough which an plug insertion operation is viewable.
 16. The apparatusof claim 15, further comprising means for discharging a fluid over thetransparent window.
 17. The apparatus of claim 12, further comprising analignment assembly provided at a lower end of the gantry assembly forsensing proximity to the well casing.
 18. The apparatus of claim 17,wherein the alignment assembly comprises:a fork which horizontallyextends from the gantry assembly; a plurality of sensors located on thefork in predetermined positions.
 19. The apparatus of claim 18, whereinthe fork has two fork members connected to provide the fork with aV-shape, and wherein the plurality of sensors are provided on facingsurfaces of the two fork members, the two fork members being oriented toaccommodate the well casing therebetween.
 20. The apparatus of claim 12,further comprising:a casing cutter mounted proximate a lower end of thegantry assembly for cutting away a portion of the well casing whichextends above a predetermined height.
 21. The apparatus of claim 20,wherein the casing cutter is pivotal about a vertical axis from a firstcutter position to a second cutter position, the first cutter positionbeing a storage position and the cutter being operable in the secondcutter position to cut away a portion of the well casing.
 22. Theapparatus of claim 20, wherein the cutter comprises a saw having arevolving saw cable of abrasive multistrand material.
 23. The apparatusof claim 1, further comprising a selectively removable flange assemblyattached at one end of the plug body and having a hollow passageway topermit fluid flow therethrough.
 24. The apparatus of claim 1, furthercomprising a protective break-away shell which circumferentiallysurrounds at least a portion of the plug body.